Flue heater



March 6, 1956 J, (5. AMES 2,737,132

FLUEI HEATER Filed May 25, 1951 2 Sheets-Sheet l J INVENTOR. dzzzea 6 220 Zd dines March 6, 1956 J. G. AMES 2,737,132

FLUE HEATER Filed May 25, 1951 2 Sheets-Sheet 2 0 0 m 1 3;? INVENTOR.

James Gerald flzzzes' W dig/ya United States Patent O FLUE HEATER James Gerald Am'es, Aurora, Ill. Application May 25, 1951, Serial No. 228,184

2 Claims. (Cl. 110-97) My invention is directed to chimneys and a novel means for reducing chimney heat losses, freeing the chimney of undesirable condensation and preventing the accumu' lation along the flue Walls thereof of soot, acids, creosote and like undesirable. substances, which greatly reduce the efliciency or the chimney and are inclined to create fire hazards.

More particularly my invention is concerned with a new and improved means for maintaining household chimneys or the like in a clean dry condition, such means having particular utility and significance in association with gas or oil fired heating plants.

The problem of preventing chimney condensation, especially in cold weather, is not a n w one in household heating. For many years householders have sought to combat the condensation problem by equipping their chimneys with metal liners of a variety of designs, most of which seek to insulate thec'himney' walls from the flue gases. The metal chimney liner has proven a satisfactory solution to the condensation problem in many cases and has the added advantage of insuring against the plugging of a flue by a falling chimneybrick or the like. However, the metal chimney liner is relatively expensive, has a limited life, usually fails only after considerable condensation damage has already occurred to the chimney itself, is not adaptable readily to oflset chimney structures, is often times not adaptable for residential gas installations,

including furnaces and other related gas appliances, and

with the non-corrosive metals normally used for such liners becoming more precious and diflicult to obtain, it is many times presently impossible for a householder to obtain such a liner. g

In addition to the metal flue liner, condensation trouble also has been combatted by adding sufiicient. heat to the flue products to revent the formation of condensation on the chimney walls. Such a practice increases heating costs, although it does eliminate the necessit of a metal liner. One such'method of heating the flue products diverts the warm basement air into the chimney fine to increase the heat of the flue gases. Past experience has proven this method successful, albeit costly, and indicates that only a small amount of heat is normally needed as an additive to the flue gases to raise the chimney wall temperatures above the dew point. One further observation is pertinent at this point When the products of combustion are discharged from the flue pipe of a furnace into a rather large chimney, as is the normal case, the velocity oflthe" flue gases is immediately and substantially decreased to a rather low value; Such low flue gas velocity results in the lack of any appreciable amount of scrubbing action of the flue gases on the chimney Walls and 'there is conse uently little cleaning action and relatively small heat transfer from the fine products to the chimney walls. Normally only the flue products immediately adjacent the chimney walls give up their heat to the chimney, leaving a hot core of gases which pass upwardly through the chimney to dissipate their usable heat into the atmosphere. For- 2,137,132 Patented Mar. 6, 1956 'ice 7 2 ther, it has been determined in the typical instance of a wet chimney, that there normally is suflicient heat in the flue products, if utilizedv to preventcondensation.

Briefly, my new and improved flue heater enables one to overcome the problem of excessive chimney condensation in an eflicient and economical manner while at the same time avoiding the above listed disadvantages of the metal chimney liner and the increased heating costs which normally accompany the method of adding more heat to the flue products. To accomplish the desirous ends of my invention I propose to block off the central core of the chimney flue and-utilize the heat of the hot flue gases, especially those present in the hot core thereof, as the hue products move upwardly, to heat the side walls of the chimney and thus maintain the chimney walls above the dew or condensation point. By effectively diverting the hot central core of the flue gases along the side walls of the chimney I am enabled to increase the velocity and scrubbing action of theflue products to effectively cause the transfer of greater amounts of heat to the chimney and thus raise the chimney wall temperature above the dew points. Additionally, the increased velocity so obtained results in a greater attritional. action along the chimney walls to effectively maintain a clean chimney.

The primary object of my invention is to demonstrate the construction and operational features of a new and improved means for heating the flue wallsof. the chimney by utilizing the normally wasted heat of the flue gases by a heat source.

A further object of my invention is to demonstrate a new and improved flue heater means which not only serves to heat; effectively the flue walls of the chimney during the operation of the heating plant, but also stores up heat to radiantly heat such flue walls when the heating plant is momentarily shut down, as in a thermostatically controlled heating system.

Still another object of my invention is to display a new and improved flue heater principle for effectively minimizing chimney condensation and for maintaining the flue walls of the chimney substantially cleaned and free of such depositsas soot, creosote, acid and the like.

The above and" further features and advantages of my invention will become apparent to one skilled in the art from the following descriptive materials and specifications and in the li hter the accompanying drawings.

In the drawings:

Figure 1 is a partial front elevational view of one type of household chimney installation in which my flue heater is adapted for use.

Figure 2 is another partial front elevational view, similar to Figure 1, displaying a second type of household chimney installation in which my flue heateris adapted for'us'e.

Figure 3 is an enlarged, foreishortened, cross sectional view of a typical chimney installation displaying my flue heater in partial front elevation as installed therein, such view being taken substantially along lines 33 of Figure l and looking in the direction of the arrows thereof.

Figure 4 is atop plan view of the flue heater installation shown in Figure 3, demonstrating in detail the features of the" mounting, hanging and spacing means for supporting and locating my flue heater in the chimney.

Figure 5 is a bottom plan view of the flue heater installation demonstrated in Figures 3 and 4 showing the means for connectively associating my flue heater with the mounting, hanging and spacing means thereof.

Figure 6 is another plan view similar to Figure 4 demonstrating the installation of a double flue heater unit made in accordance with the teachings of my invention, especially adapted for chimneys having an elongated rectangular top profile.

Figure 7 is a partial foreshortened cross sectioned front elevational view similar to Figure 3 showing the double flue heater of Figure 6 in foreshortened elevation therein and demonstrating my spacing, hanging and mounting means associated therewith.

Figure 8 is a bottom plan view of the double flue heater demonstrated in Figures 6 and 7 showing in detail the means for connectively associating my flue heater with the mounting and spacing means thereof.

Corning now to the details of the construction of my flue heater 10 adapted for utilization with an outside chimney, such as is illustrated in Figure 1 or 2 of the drawings, it will be observed from Figure 3 that my flue heater unit therein illustrated is adapted to be mounted centrally within the interior of flue chamber of a chimney 11 in a vertical hanging position substantially as illustrated. The single flue heater unit 10, illustrated in Figure 3, comprises essentially a plurality of vertically aligned core block sec tions 12 formed, in the illustrated instance, with a substantially rectangular profile as seen in Figure 4. This sectional block construction is primarily designed to meet limitations as to handling the material, and it will be appreciated that a single elongated core may be utilized in my construction with equal effectiveness. The material I prefer for the core block members 12 is alight and durable impervious insulating vitreous material manufactured by the Pittsburgh Corning Corporation of Pittsburgh, Pa., and sold under the trade name of Foamglas Insulation. This material is particularly adapted for the purposes of which I am about to describe because of its extreme lightness, low cost, and ability to absorb or retain heat during the normal operation of the household heating unit for later radiantly heating the chimney flue side walls when the furnace is secured momentarily. The Foamglas Insulation product is essentially composed of a vitreous glass material which is impregnated with a suitable gas, such as hydrogen sulphide, which reacts therewith during a special process known to the Pittsburgh Corning Corporation to form a very light but impervious honey-comb structure in which the cellular walls of the structure entrap small pockets of the gas.

Other materials may be utilized for the purpose of the flue heater core blocks 12 as well. Since the main purpose of the flue heater is to efiectively block off the upper central core of the chimney flue, any suitable impervious material such as aluminum, or like light metal, sheet steel, fire-proof treated wood or concrete, phenolic resin plastic, a combination of asbestos and concrete cast together under pressure similar to the Johns Manville product Transite, or like related substances are also adaptable for this purpose, although I prefer the impervious Foamglas product illustrated. In relation to the alternate named materials, I have found it particularly useful to form them into hollow tubular or elongated rectangular shapes having the ends thereof blocked off so as to form a heat retaining chamber within their interior, thus adapting them for the radiant heating feature prevalent with the Fo amglas core block material described above. The wood and concrete may be formed as solid elongated blocks if desired, but such materials are not to be preferred because of weight considerations.

As will be recognized from Figure 3, the several flue heater core block elements 12 are held together in aligned vertical relation by means of a pair of hanger rod members 13 mounted vertically therethrough in side-by-side parallel spaced relation to form a rigid rectangular block or core structure. It also will be recognized that each of the rods 13 is bent over in right angular relation at its upper end to be received within a suitably shaped interior opening 14 of a cast aluminum cap member 15, or the like, as illustrated; two such cap members being utilized to each of the single heater units as shown in Figures 3 through 5. Each of the cap members 15 is further provided with a transverse opening 16 above the opening 14 thereof for the reception therethrough of a horizontal suspension rod 17, of suitable dimensions, and upon which the weight of my flue heater is supported. It will be recognized that the rod 17 is adapted to reach substantially across the outside dimensions of the mouth of the chimney 11 and is held in position in the spaced apart cap members 15 by means of suitable set screws 18 associated therewith, illustrated in Figures 3 and 4.

The lower end of each of the hanger rods 13 is provided with flanged metal nut member 19, herein shown as cast with a circular flange portion 20 and a projecting central sealed-over nut portion 21 provided with internal threads for the threading reception therein of the threaded lower end of its associated rod 13. Two such flanged nut members are provided for each of the single heater units, as illustrated in Figure 3, such nut members corresponding in number to the number of rod members 13 associated with the heater unit and serving to transmit the hanging Weight of the above positioned core blocks to the two vertical hanger rods 13. It will be observed that by the provision of the sealed-over nut portion 21 flue gas is deterred from entering the internal structure of the several core block members 12 and the lower ends of the rods 13 are thus effectively sealed over from contact with the caustic and corrosive action of the flue gases. Preferably, the flanged nut member 19, cap members 15, hanger rods 13 and the horizontally disposed suspension rod 17 are all made of aluminum, such material being resistant to the chemical effects of the flue gases. Intermediate the flange nut members 19 and the holding caps 15, at the intersection of the several core block sections 12,.I have provided a plurality of spaced apart spacing brackets 22; disposed so as to protrude outwardly on opposite sides of my heater 10. Each of the brackets 22, as illustrated in Figures 3 and 4, comprises a thin substantially rectangular shaped plate or" cast aluminum or the like through which the rods 13 are adapted to be inserted transversely as illustrated for securing the brackets 22 in position between adjacent core blocks 12. An external holding head member 23 is associated with each of the spacing brackets 22; such being provided with two openings disposed in transverse oif-set relation one above the other. Such openings in each holding head member 23 are provided for the reception therethrough of one long cylindrical spacing rod member 24 and one short spacing rod 25 which acts as spacers for centrally locating my heater member within the flue chamber of the chimney 11. In this latter connection, it will be noted that the longer rods 24, as illustrated in Figure 4, extend transversely of the width of the flue opening 26 of the chimney 11 while the shorter rods 25 are adapted to reach in an opposite transverse relation to the rods 24. The several rods 24 and 25 are suitably held in their spacing positions by means of set screws 27 or the like threadingly associated with the holding head members 23.

It further will be recognized that the number of spac- 7 ing brackets 22 with their associated spacing rods 24 and 25 is not critical, but is entirely dependent on the overall length of the heater core member comprising the several aligned block members 12; there being two such brackets 22 between each pair of adjacent core blocks 12.

It also should be noted that the two flanged nut members 19 are each provided with four raised boss members 30, 31, 32 and 33 arranged in diametrically opposed pairs. As with the holder members 22, the several bosses are provided with a transversely extending spacing rod member for the purposes of locating the lower end of the heater core centrally in the chimney flue; bosses 30 and 32 each being provided with a long spacing rod 34 and each of the bosses 33 being provided with similar transversely extending short rod member 35 similar to the short rods 25. The two boss members 31, which are positioned adjacent one another nearest the longitudinal central axis of the core heater, are interconnected by a suitable wire or rod fastener 36 for retaining the nut members 19 against rotation after assembly of the heater, as described heretofore.

To mount a flue heater 10, as I have described above, within the flue chamber of a chimney 11, it is merely necessary to insert the same from the upper end of the chimney, thrusting the heater downwardly to effectively block over the upper central core area of the flue; the heaters central position being maintained by the several locating rods 24, 25, 34 and 35 as described. It further will be recognized that the several mounted spacing rods are designed to reach a distance slightly greater than the cross sectional dimensions of the flue opening 26. so that upon thrusting my heater into the chimney flue, the locating rods are flexed slightly upward with a springing action to resiliently locate and hold the; heater in position. The transverse suspension rod 17, of course, rests on the upper lip of the chimney side walls, as illustrated in Figure 3. In connection with the flexing actuation of the several locating rods, this particular design has been found to be exceedingly well adapted for mountingmy flue heater as described,since in many chimneys the interior surface of the flue is rough, accompanied by secreted mortar spots, pits, and the like. A rigid locating rod or bar means is greatly inclined to hang up or jam on the rough interior of the flue giving the installation personnel undue hardship in installing my unit.

With reference to Figures 6 through 8, it Will be recognized that the single heater unit 10, as described heretofore, is not adaptable for all sizes of chimneys and in special cases wherein very Wide flue opening is. encountered, it is desirable to install a large heater unit, such as unit, 40 illustrated in Figure 7. It will be observed that the large unit 40 of Figure 7 comprises essentially two of my single units 10 placed side-by-side and fastened together. Since added size means a corresponding increase in weight, the heater unit 40 is fitted with two horizontal suspension rods 17 as described heretofore. The various locating means, hanger rods 13, flanged nuts 19, and like, elements of the heater are identical for both constructions. It will be recognized from Figure. 8, however, that in addition to. the normal wire or rod fasteners 36, which reach between the adjacent bosses 31 of flanged nut mem ber 19, other similar fasteners 41 are utilized for fastening the two single units together; such being fastened between bosses 32, of the several nuts 19 as shown. Additional holding support for maintaining the two single heater units in side-by-side relation is accomplished by inserting the locating rods 24 through two of the holding brackets 22 correspondingly associated with the separate core block members 12 of the two side-by-side single heater units. It further will be recognized that if conditions demand, more than two of the single heater units may be assembled, similar to the manner illustrated in Figures 6through 8, to meet larger sized flue openings.

Having thus described the structural features of my novel flue heater, it will be recognized that it has universal adaptability for chimneys of various sizes and shapes, and that, although a rectangular core member has been illustrated, other shapes may be used with equal facility.

USE. AND OPERATION In installing a fine heater as I have described heretofore, it is necessary to bear in mind several important limiting factors. Initially, since my flue heater effectively blocks off the core of the chimney flue, it is essential that its rectangular dimensions be so designed as to permit efiicient draft action of the chimney. To this end, I

that in most instances a flue heater having a minimum length of four feet. will be; satisfactory and serve effective 1y to maintain a chimney free of condensation.

Further, it is desirable, although not essential, that in cases where an outside chimney is involved, such as illus trated in Figures 1 and 2 of the drawings, that my flue heater reach substantially the length of the exposed portion of the chimney, that is, that it be long enough to reach into the building.

It also should be borne in mind that in many cases the chimney is so poorly designed as to be unadaptable for the installation of a. heater in accordance with the teachings of my invention, and in fact may be such a design as to be unadaptable for any type of flue heater. In this connection, it should berecognized that the net area available in the chimney flue should at all times be as large or larger than the sum of the. areasof all flue pipes of appliances vented into the chimney, or inother words,

a the cross sectional area of my flue heater should be no greater than the difference betewen the cross sectional area of the fiue opening minus. the total sum of all the cross sectional areas of the flue pipes which discharge into the. chimney flue. Expressed in other terms, the net available B. t. u. output of the chimney, with my flue heater installed, should be. no less than the total B. t. u. input discharged into the chimney for effective and eflicient operation of the chimney flue. At the same time, it should be borne in mind that the distance between the side. walls of the chimney flue and, the nearest point to my radiant flue heater should normally be no less than 1 /2 inches. Also, in determining the cross sectional dimensions of my flue heater, it should be remembered that its. designed cross sectional area should be based on; contemplated future installation of various appliances, such as a household water heater, stove or the like, so that in the event only a furnace isv presently discharging into the chimney flue, suflicient' leeway remains to permit the installation of later appliances and their discharge into the flue. For example, based on Y a standard flue capacity of 5,000 B. t. u.s per hour per square inch of cross sectional area, a flue bearing the cross sectional dimensions, of 10 x 10 inches would have a total B. t. u. capacity of 500,000 B. t. u.s per hour. If, for example, the total B. t. u. discharge into the flue were 200,000 B. t. u.s per hour, the maximum cross sectional size of my flue heater that could be utilized would be 6.0 square inches. The figure 60 square inches, converted into B. t. u. capacity, based on the 5,000 B. t. u. per square inch capacity figure, would mean that the flue heater would elfectively block off and reduce the capacity of the flue by 300,000 B. t. u.s which would result in the B. t. u. input into the flue being equal ever, bearingin mind the limitation that for practical design purposes at least 1 inches should exist between my flue heater and the side walls of the chimney, a block bearing the dimensions of 7 x 7 inches square is to be preferred. Converting the 7 x 7 inch flue heater dimensions into B. t. u. capacity based on the standard 5,000 B. t. u./sq. in. capacity figure, this flue heater would effectively block off 7 x 7 or 49-square inches 5,000 B. t. it. per square inch or 245,000B. t. u. per hour, which leaves a net flue capacity then of 255 B...t. 11. per hour which gives an effective safety margin of 55 B. t. u. per hour available for the later installation of additional appliances discharging into the chimney flue. at a rate not, to exceed $5,000 B. t. 1.1. per hour. total. The 7 X 7 inch mension then for my flue. heater would be satisfactory inthis instance.

For further examplesof selecting the proper flue heater size see the. table listed below:

Selecting radiant flue heater Chimney Flue Radiant Flue Heater Option 1, 1 6 spacers Option 2, 2 spacers Option 3, 3 spacers Size, Capacity Effective Flue Effective Flue Effective Flue Inches (13. t. uJhr.)

Ca acity Capacity Capacity Sm (B. 1i. u./hr.) (13. t. 111m. (B. t. mm.

A B O D E F max. G H max. 12 x12 720, 000 9 X 9 315, 000 8 x 8 400, 000 6 X (3 e40, 000 12 x 10 600, 000 9 x 7 285, 000 8 x 6 360. 000 6 X 4 480, 000 10 x 10 500, 000 7 x 7 255,000 6 x G 320, 000 4 X 4 420, 000 10 x 8 400, 000 7 X 5 225, 000 6 x 4 280, 000 4 x 2 360, 000 8 X 8 320, 000 5 X 5 195, 000 4 X 4 240, 000 2 x 2 300, 000 8 x 6 240, 000 5 x 3 165,000 4 x 2 200,000 6X 6 180, 000 3x3 135,000 2X 2 100, 000

Explanation:

(1) Flue capacities based on 5000 B. t. u. per square inch. (2) Columns D, F, and H show maximum capacities of flue with heater installed.

To more fully comprehend the workability of my in vention, it may be helpful to study the results of a few actual field installations of this device.

EXAMPLE I Chimney cnditi0ns.-Flue 9" x 13", single course brick, outside above first floor of a two story house.

Operational c0nditions.--With outdoor temperature at 52 F. the gas burner of the heating installation having a 95,000 B. t. u./hr. output was turned on. After one hour, stable conditions in the stack were reached with the stack temperature of 400 F. existing at the inlet draft diverter and 170 F. at the outlet of the chimney. At the starting condition the temperatures within the chimney at the outlet, ten inches down from the top, were 77 F. at the brick face, 86 F. at a point one-quarter inch away from the face, and 140 F. at the flue center.

Flue heater eflect.--A flue heater made in accordance with my invention having the cross sectional dimensions of x 9 inches and 48 inches long was installed in the upper end of the chimney flue; the spacing between the sides of flue heater and chimney flue being a uniform 2 inches. After conditions had stabilized the temperature within the chimney flue, inches down from the top, was 95 F. at the brick face showing an increase of 18 F.; the temperature one-quarter inch away from the brick face toward the center of the flue was 131 F. or an increase of 42 F.; and the temperature one inch away from the brick face was 149 F. or an increase of 9 F.

Conclusions.l. The temperature at the center of the flue was 63 higher than at the brick face before installing the flue heater.

2. The volume of the flue products was obviously very high at the core of the flue stack.

3. After the flue heater was installed the temperature one-quarter inch away from the brick face rose 42 F. indicating that a very considerable amount of heat had become available for keeping the brick face of the chimney above the dew point to prevent condensation.

4. At no time during the test was there any evidence of condensation.

EXAMPLE II Chimney conditi0ns.-The chimney was a single course unlined brick chimney with the flue from the basement to the top of the second story having cross sectional dimensions of 4" x 22 /2" and from thence upward it became wider until 4% ft. outdoor portion had a flue dimension of 9" x 22 /2.

Operational conditions.With an outside temperature of F. the gas burner in the household heating installation having a 115,000 B. t. u./hr. output was turned on. After about one hours operation the core temperature in the chimney flue 10" down from the top was 82 F. The chimney flue itself was extremely wet on the outside as well as the inside, with condensation coming through the chimney mortar to wet the outside. A thick layer of frost existed at the top of the chimney.

Flue heater efiecz.A radiant flue heater of my invention having cross sectional dimensions of 6" X 19" and a length of 48" was installed and after one-half hours operation the temperature adjacent the flue face was 94 or an increase of 12 F. After one and one-half hours operation the frost on top of the chimney disappeared and the top layer of bricks has become dry. However, the chimney flue remained wet at that point.

One day later, after continuous operation of the chimney with my flue heater installed and with atmospheric temperature of 30 F., the second layer of brick down from the top of the chimney had become completely dry, the outside of the chimney was completely dry, with the balance of the chimney apparently drying nicely inside.

Three days after installing my flue heater, the inside top three layers of bricks were completely dry, the radiant flue heater was hot and dry to the touch and remained warm between burner cycles with a strong current of Warm dry air flowing around the heater and up the chimney flue.

At the end of the tenth day of operation with the atmospheric temperature raised to 50 F. the chimney flue became completely dry. With the burner off a very good stream of warm dry air blasted into the observers face with the radiant flue heater itself being very warm and dry.

During the succeeding six days, at which time the atmospheric temperature had lowered in the neighborhood of 0 F., the chimney remained completely dry with a bedroom wall on the second fioor of the house, which had previously shown considerable condensation damage, now being completely dry.

C0nclusi0ns.1. At the start of this test the chimney itself was soaking wet inside and outside with condensation moisture coming through the bedroom wall and the core temperature of the flue being in the neighborhood of 82 F.

2. The burner input was only moderate, leaving only a small amount of available heat for drying purposes with the chimney being of a very large size to further complex the drying problem.

3. The accomplishment of completely drying the chimney in only ten days showed convincing evidence of the drying ability of my flue heater and the continued operation thereof during the subsequent 0 F. weather proved that the flue heater could maintain the chimney dry even in extreme cold conditions.

4. Further, by drying the outside of the chimney during the very cold Weather, it is evident that my flue heater tends to prevent frost action which damages chimneys above the roof line in contrast to the effect of a action.

EXAMPLEv III Chimney conditions-The chimney was an inside chimney having a clay tile flue of 6%" x 11 /2" cross sectional dimensions.

Operational enditi0ns.With the outside temperature at 29 F. the heating installation gas burner having a 114,000 B. t. u./hr. output was turned on. In about one hour conditions were stabilized with the outlet draft diverter temperature being 220 F. and the chimney temperatures varying from 110 F. one-quarter inch away from the brick face, down from the top to 120 F. at the core or center of the flue. Condensation had formed about 10" down from the top on one side of the chimney, first in the form of drops and later in the form of a continuous flowing stream; The moisture had deposited on one other side of the chimney as well butnot to a considerable extent.

Flue heater efiecL-After installation of my flue heater having cross sectional dimensions of 3" x 8" and a length of 48", the flue temperature one-quarter inch away from the brick face and 10 down from the top was at 116 F. and at a distance three-quarter inches away from the brick face was at 120 F. The moisture previously formed in the chimney completely disappeared after 30 minutes of operation with my flue heater and at the end of one hours operation all trace of moisture had disappeared with the chimney and flue being very dry.

A subsequent inspection of this same chimney was made thirteen days later with the outside atmospheric temperature being at a -2 F.; the chimney having 0perated continuously during the intervening period with my flue heater installed. The chimney was found to be perfectly dry with the inside surface. being definitely warm. The flue heater itself was in the neighborhood of from 80 to 100 F. during the off-cycle of the burner.

C0ncZusi0ns.-The general conditions of this chimney indicate that under ordinary conditions and circumstances this chimney would present a definite condensation problem and that the installation of the flue heater served to keep the chimney in a perfectly dry condition even at the extreme low temperature of 2 F.

EXAMPLE IV Chimney c0nditi0ns.The chimney in this instance was an outside chimney having a clay tile lined flue and was completely exposed for feet of its upper length. Flue dimensions were 7" X 11 /2".

Operational c0nditi0ns.--The heating installation gas burner having a 120,000 B. t. u./hr. was operated for about one hour and at that time the temperature near the core of the flue was approximately 114 F. The inside chimney flue was very wet down as far as could be observed from the top thereof. The atmospheric temperature was F.

Flue heater efject.-After installation of my flue heater having a cross sectional dimension of 4" x 8" and a length of 4 in the chimney flue; the temperature near the inside brick face of the chimney flue was 116 F. After about one hours operation, part of the clay tile liner extending above the chimney was hot and dry but the chimney otherwise remained wet. The flue heater felt hot, especially while the burner was in operation.

Three days later the chimney was apparently dry for a distance of about 3 down from the top of the chimney with only a few drops of condensation appearing on the tile liner. At that time the flue heater was very warm and there was a good flow of warm dry air up the chimney flue. During the intervening three day period the atmospheric temperature had varied from a 0 F. to 32 F.

Nine days later the chimney was no longer definitely wet. and to initial observation appeared dry, but the ruhhing. of the, surface showed some moisture was still present. With the burner off a very good stream of warm dry air continued to blast into the observers face and the flue heater itself was very warm and dry. At this observation the atmospheric temperature was 50 F.

Seventeen days after the installation of my radiant flue heater, the chimney was observed with the atmos-- pheric temperature being 15 F. At this time the chimney was completely dry which was especially significant since the atmospheric temperature during the six preceding days. had varied from 0 F. to 10 F. At this seventeenth day observation the radiant flue heater was very Warm and the flue products were warm. and apparently dry.

Six days later a check observation was made of this chimney during which six days the atmospheric temperature had remained under 0 F. with the observation showing that the chimney was in an extremely dry condition.

Conclusions-l. As mentioned above, this, was an extreme case involving an outside chimney having 15' of completely exposed length.

2. When the test was started the chimney was soaking wet as far down as could be observed.

3. After the installation of a flue heater, made in accordance with my invention the drying ability of the flue heater was completely established and there was a complete drying of the chimney within 17 days.

4. It. was further observed, during an extreme succeeding cold weather period, that the flue heater could maintain this outside chimney dry even during, severe weather conditions.

From the foregoing examples it will be recognized that a flue heater made in accordance with the. teachings of my invention, and based on the principle of effectively blocking off the hot core area of theflue gases and diverting such gases outwardly along the side walls of the chimney flue to create an increased velocity thereof and a more eflicient scrubbing action, results in a new and improved means for maintaining a chimney, even under extreme weather conditions, substantially free of condensation. It further will be recognized that when the flue heater of my invention is constructed of light materials which are nevertheless impervious to penetration of flue gases, such as the herein specified Foamglass Insulation made by Pittsburgh Corning Corporation of Pittsburgh, Pa., an advantageous effect of radiantly heating the chimney walls during the periods when the household gas burner, or the like, is shut down is also available. Other means of gaining this radiant heating eiiect are also available as suggested and the combination of such radiant heating effect with an accelerated gas flow and scrubbing action results in an improved flue heater as taught herein.

Further, it should be recognized that the flue heater of my invention has the combined advantages of being low in cost, being extremely easy to install, requires no special skill for installation, furnishes protection to the home owner against blocked flues from falling or loose bricks (which experience shows in to of all cases vto involve bricks coming from the upper part of the chimney), to be suitable for use with oil fuel as well as gas fuel, to be adaptable for all types of chimneys including olfset chimneys and to be easily removable from the chimney if necessary.

Further, it should be recognized that the structural features of my flue heater are extremely simple and by combining several of the single type of units, illustrated in Figures 3 through 5, it is possible to adapt my flue heater to practically any size of chimney flue opening,

such as I have illustrated in Figures 68 of the drawings.

While I have herein shown and described two forms in which the teachings of my invention may be embodied, it will be appreciated that various changes, modifications and substitutions of equivalents may be made therein without departing from the spirit and scope of my invention. Further, while I have specified several materials out of which the core block of my flue heater may be constructed, it will be recognized from their diverse properties that any material which is substantially impervious to penetration of flue gases and has the ability of absorbing a suflicient quantity of heat to provide a radiant heating effect during the off burner period of the household heater operation will be adequate and acceptable in most instances. To gain a successful material for my flue heater, it is most desirable that such be as light as possible, similar to the Foamglas material specified hereabove. It will, therefore, be appreciated, in view of the novel aspects of my invention, that I do not wish to be limited to the specific embodiment herein illustrated and described except as may appear in the following appended claims.

I claim:

1. A flue heater of the class described for dispelling condensation in household chimneys or the like, comprising in combination, an elongated impervious core member, hanger members extending vertically through the interior of said core in spaced apart parallel relation, a cap member connectively mounted at the upper end of each of said hanger members, a horizontal suspension rod mounted transversely through both of said cap members and adapted to reach substantially across outside dimensions of the upper end of said chimney to support the weight of said core member thereon, flange nut means threadingly mounted at the lower ends of said hanger members for rigidly connecting the latter with said core member and sealing over the lower ends of said hanger members, a plurality of bracket members mounted transversely of said core, intermediate the length thereof and protruding transversely outward therefrom, and a plurality of spacing rod members supported in said bracket members and adapted flexibly to engage the side walls of said flue for positioning and mounting said heater centrally within the upper end of said chimney to block ofi the central passage area of said flue.

2. A chimney flue heater, insertable vertically as a removable unit within a chimney and from the upper end thereof, comprising in combination, an elongated core member consisting of a plurality of vertically aligned rigidly interconnected sectional block members of impervious material, suspension rod means reaching across the mouth of said chimney above said core member, hanger means connecting said core member with said suspension rod means whereby the weight of said core member is supported by said suspension rod means and said hanger means serve to maintain said block members in adjacent vertically aligned relation, and a plurality of resilient spacer means mounted along the sides of said core member, protruding laterally outward therefrom and extending into the interior thereof between adjacent block members, said spacer means having resilient engagement with the interior flue side walls of said chimney to effect ready insertion and withdrawal of the flue heater, said spacer means serving centrally to locate said core means within said chimney flue thereby to block over the central cross sectional area of said flue and cause flue gases emitting from said chimney to flow divergently therearound and upwardly along the interior side walls of said flue to transfer heat thereto.

References Cited in the file of this patent UNITED STATES PATENTS 1,348,032 Moody July 27, 1920 2,081,612 Woodson May 25, 1937 2,156,101 Willett et al Apr. 25, 1939 2,215,538 Blauvelt Sept. 24, 1940 2,411,504 Carlise Nov. 26, 1946 2,570,948 Hinsley Oct. 9, 1951 

